Anchor bolt

ABSTRACT

An anchor bolt for clamping an object tightly against a receiving surface comprises a threaded elongated anchor rod having a head, an expansion body threadedly received on the rod in spaced relation to the head, and an expansion sleeve on the expansion body that is expanded as the rod is threaded into the expansion body. The anchor rod extends through an outer sleeve between an abutment on the head and an abutment on the expansion body, and spacers, such as a coiled spring or further sleeves, are provided between the anchor rod and the outer sleeve. The bolt provides improved shear resistance and anti-vibration efficiency.

FIELD OF THE INVENTION

The present invention relates to an anchor bolt for engagement in asocket in a receiving material, thereby to clamp an object, such as aprofiled beam, to the material.

BACKGROUND ART

Such an anchor bolt normally comprises a threaded anchor rod which isprovided with an expansion body at its threaded end on which is mountedan expandable sleeve, the body being structured so that as the anchorrod is moved axially of the expansible body, with the head of the rod inabutment with the object to be clamped, the sleeve is expanded intogripping contact with the socket.

It is known to position a tubular sleeve between the head of the anchorrod and the expansion body, the tubular sleeve occupying the spacebetween the inner wall of the socket and the rod thus enabling theanchor bolt to withstand high shear loads.

In practice a hole of the required diameter is first drilled in thereceiving material and the anchor bolt is hammered into the drilled holethrough a correspondingly sized hole in the object to be clamped.

The anchor rod is then torqued-up thereby to set the anchor bolt. Oncethe required anchorage has been achieved further axial movement of therod is impeded because the sleeve is in abutment both with the expansionbody and the head of the anchor rod.

When this condition is achieved, no axially acting force componentremains available to enable the object to be clamped to be pulled downagainst the receiving material.

SUMMARY OF THE INVENTION

It is an object of the invention therefore to remove the disadvantagesof the prior art by providing an anchor bolt which while having theability to withstand high shear loads, ensures that the object beingclamped is pulled down against the bare material so that the fixing isable to withstand vibrational loads.

According to the invention there is provided an anchor bolt forengagement in a socket in a receiving material to clamp an objectthereto and comprising a threaded anchor rod, an expansion bodythreadedly received on the rod, an expansible sleeve on the expansionbody and expandable into gripping contact with the socket as the rod ismoved axially therein to draw the body into the sleeve, an abutment onthe expansion body and the head of the rod, at least one sleeve betweenthe abutments in spaced relation with the rod and dimensioned to bridgeor substantially bridge the abutments when the bolt is anchored in thesocket and the object is pulled hard against the receiving material, andspacer means between the abutments on the rod over which the sleeve canslide during said axial movement of the rod to reduce the distancebetween the abutments such that the space between the sleeve and the rodis occupied or substantially occupied by said spacer means when the boltis anchored in the socket.

This arrangement obviates the deficiencies of the prior art anchor inthat the distance between the respective abutments progressively reducesfrom the moment the anchor rod is turned in the expansion body first toset the expansion sleeve to the required torque, and then to reducefurther axially until the object to be clamped is brought firmly againstthe receiving material and the sleeve occupies or substantially occupiesthe distance between the abutments.

Due to the fact that the spacer means is between the outer sleeve andthe anchor rod in the anchored or set position, a solid or substantiallysolid body is formed between the internal surface of the socket and thebody of the anchor rod thereby providing the required ability towithstand high shear loads, while the induced load in the bolt from thetorque tightening remains substantially to clamp down the fixture andhence maximise the anti-vibration efficiency.

Preferably the spacer means is a coiled spring held between the abutmenton the expansion body and the rod head.

Alternatively the spacer means may comprise a pair of spacer sleeves oneof which is press-fit within the outer sleeve and in abutment with theanchor head, the other spacer sleeve being arranged for slidablemovement within the outer sleeve as the distance between the abutmentsis reduced.

The outer sleeve and the first and second spacer sleeves are preferablylongitudinally split tubes, the second spacer sleeve abutting theabutment on the expansion body and of lesser outside diameter than theoutside diameter of the first spacer sleeve which is positioned withinthe outer sleeve in press-fit engagement. Thus the outer sleeve assumesa tapering effect, with the maximum diameter of taper being adjacent theabutment at the head of the rod and of slightly greater diameter thanthe receiving socket.

In this way, with the anchor bolt fully tapped home in the socket priorto torquing-up, the outer sleeve is firmly engaged in the socket at theposition of maximum taper so preventing the sleeve falling out of thesocket when the anchor bolt is used in an overhead application, or ifthe rod is removed after the anchor has been set.

Other features and advantages of the present invention will becomeapparent from the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample with reference to the accompanying drawings wherein:

FIG. 1 is a view of an anchor bolt according to an embodiment of theinvention;

FIG. 2 is a cross-sectional view of an anchor bolt according to anotherembodiment of the invention and includes a sectional view through thesplit tube assembly of the bolt;

FIG. 3 is a cross-sectional view through an anchor bolt according toanother embodiment of the invention;

FIG. 4 shows an anchor bolt according to a further embodiment of theinvention and includes a cross-sectional view through the bolt;

FIG. 5 shows a part cross-sectional view through an anchor boltaccording to another embodiment of the invention;

FIG. 6 is a cross-sectional view through an anchor bolt according to astill further embodiment of the invention; and

FIG. 7 shows the anchor bolt of FIG. 4 mounted in-situ and clamping anobject to bare material.

BEST MODES OF CARRYING OUT THE INVENTION

The anchor bolt shown in FIG. 1 comprises a threaded anchor rod 1 havinga head portion 2 shaped to enable torque to be applied to the rod whensetting the anchor bolt.

An expansion body 3 is threadedly received on the anchor rod 1 and has aleading circular head portion 4, a trailing circular head portion 5 anda waisted portion 6 between the head portions 4 and 5 which taperstowards the head 2 of the anchor rod 1.

An expansible tubular split sleeve 7 is mounted on the waisted portion 6and is of substantially the same diameter as the head portions 4 and 5.

The head portion 5, and the head 2 of the anchor rod 1, form abutmentsbetween which is held a coiled spring 8. Normally a washer 9 isinterposed between the spring 8 and the head portion 2 as shown.

A plain tubular sleeve 10 of the same diameter as the portions 4 and 5and sleeve 7, is mounted over a portion of the spring 8 and in abutmentwith the washer 9.

The anchor bolt as above described operates when used to clamp an objectsuch as a profiled beam to receiving material, as follows.

A socket of the diameter of the head portions 4 and 5, the sleeve andthe plain tube 10, is first drilled in a receiving material. A similarhole is drilled, or pre-drilled, through the object to be clamped.

The anchor bolt is then inserted through the hole in the object to beclamped and tapped home in the socket. Application of torque to the head2 of the anchor 1 causes the expansion body 3 to be drawn axially of theanchor rod 1 thereby expanding the sleeve 7 into gripping contact withthe socket to thereby set the anchor bolt. Axial movement of theexpansion body 3 during this torquing-up action correspondingly reducesthe distance between the head portion 5 and the end of the sleeve 10,and compresses the spring 8. The sleeve 10 is longitudinally dimensionedso that subsequent rotation of the anchor rod 1 in the expansion body 3further reduces the distance between the sleeve 10 and the abutment 5until the object to be clamped is firmly held against the receivingmaterial, at which point, the end of the sleeve 10 is in contact with orpreferably almost in contact with the abutment or head portion 5.

The combination of the sleeve 10 and the compressed spring 8, spacedbetween the sleeve and the shank of the anchor rod 1, in the setcondition of the fixing provides the anchor with the ability towithstand high shear loads. This coupled with the fact that the objectto be clamped is held firmly against the bare material provides all theadvantages which the prior art does not possess.

Moreover since the sleeve 10 does not come into contact with the headportion 5 before the object to be clamped is firmly held against thereceiving material, any torque loading applied to the anchor rod 1 in aneffort to achieve this end, does not go to otherwise uselessly loadingthe sleeve 10 as with the prior art device, but rather to improve thegripping action of the anchor rod by introducing stress forces actingbetween the head of the anchor rod 1 and the expansion body 6 throughthe bare material and along the rod itself to the expansion body 3, andthus between it and the sleeve 7. In this way the anti-vibrationalproperties of the fixing as a whole are maximised.

The anchor bolt shown in FIG. 2 is a modification of the anchor boltshown in FIG. 1, the modification being exemplified in thecross-sectional view of the bolt shown. In this example of theinvention, as with the further embodiments to be described, those partsin common with the embodiment of FIG. 1 will be given like referencenumerals.

Thus in FIG. 2 the coiled spring 8 abuts an inner longitudinally splittubular sleeve 11 interposed between the spring 8 and the washer 9.

The inner split sleeve 11 is in friction fit with an outerlongitudinally split tubular sleeve 12 of greater longitudinal extentalong the axis of the rod 1 than the inner sleeve 11, and positionedover the coiled spring 8.

The arrangement of the longitudinal splits 11' and 12' in the sleeves 11and 12 is shown in the cross-sectional view through the split sleeveassembly in FIG. 2. The splits 11' and 12' are arranged to bediametrically opposed as shown although this is not essential.

The presence of the inner sleeve 11 while retaining the coiled spring 8within the assembly, serves to fully support the bolt when in shear.

The splits 11' and 12' are introduced so that the sleeves 11 and 12 maybe made from strip material and to improve the interference fit betweenthe two sleeves since any variation in diameter is taken up by theinduced resilience of the respective split sleeves.

In the embodiment of anchor bolt shown in FIG. 3, the whole of thecoiled spring between the head portion 5 and the head 2 of the anchorrod 1 is enclosed. This is provided by adding an additional tubularinner split sleeve 13 for movement within the outer tubular split sleeve12 in the embodiment of FIG. 2.

While this arrangement reduces the influence of grit entering betweenthe coils of the spring 8, nevertheless due to the need to make theadditional sleeve 13 of thin section so that the maximum diameter of thespring 8 and the thickness of the outer sleeve 13 may be retained, thereis a tendency for the assembly to seize up during movement such thatfull travel can not be ensured.

The embodiment shown in FIG. 4 removes these dangers by dispensing withthe coiled spring and introducing an additional inner longitudinallysplit tubular sleeve 14 movable within the outer tubular sleeve 12. Thisis shown clearly in the cross-sectional view shown in FIG. 4. Thelengths of the sleeves 11 and 14 are such that when the anchor bolt isfully torqued-up and the object to be clamped is firmly against thereceiving material, the sleeves 11 and 14 are in abutment, orsubstantially so, within the outer sleeve 12 thus introducing soliditybetween the wall of the socket and the anchor rod 1.

In the embodiment of FIG. 4 the additional sleeve 14 is of lesserdiameter that the inner sleeve 11 such that the outer sleeve 12 forms atapered configuration the tapering direction being towards the expansionbody 3.

Additionally the diameter of the inner sleeve 11 is such that thediameter of the outer sleeve 12 at this point is a little greater thanthe diameter of the drilled receiving socket. In this way when theanchor bolt is tapped home in the socket the sleeve is held in frictiongrip in the socket so that it will not fall out of the socket in anoverhead application, upon removal of the anchor rod 1.

While the arrangement of FIG. 4 ensures that a portion of the outersleeve 12 is in friction fit with the socket, the modification shown inFIG. 5, while retaining the tapering properties of the outer sleeve 12,is designed so that the whole extent of the outer surface of the sleeve12 is in friction fit with the receiving socket in the fully clampedposition of the anchor bolt.

To this end the additional sleeve 14 of FIG. 4 is provided with amid-section belled-out portion 15' so that as the outer sleeve 12 movesover the surface of the additional sleeve 14 it is wedged outwardly intogripping contact with the receiving socket.

Due to manufacturing restrictions the length to which the split sleevesof the anchor bolts as described hereinbefore may be made, isrestricted. This restriction is overcome by the embodiment shown in FIG.6.

This arrangement comprises two longitudinally split outer tubularsleeves 15 and 16 spaced from one another and each being in abutmentrespectively with the head 2 of the bolt 1 and the head portion 5 of theexpansible body 3.

A shorter split inner tubular sleeve 17 is held in press-fit engagementat the end of the sleeve 15 and in abutment with the washer 9 or head 2of the anchor rod 1, while a split inner tubular sleeve 18 of similardimensions is held in press-fit engagement within the outer sleeve 16and in abutment with the head portion 5.

A further split inner tubular sleeve 19 for sliding movement within theouter sleeves 15 and 16, is situated centrally between the head portion5 and the washer 9 or head 2, as shown. The relative dimensions of theinner sleeves 17, 18 and 19 is such that with the bolt fully torqued-upand the object to be clamped held hard against the receiving material,the sleeves 15, 16 abut or substantially abut one another, and thesleeve 19 is both in abutment with the sleeves 17 and 18, therebyforming a solid or nearly solid piece of material between the receivingsocket and the anchor rod 1.

The centrally situated inner sleeve 19 can be modified according to thesleeve 15' of the embodiment of FIG. 5 and of lesser diameter at itsentrant portions into the sleeves 15 and 16, to provide the taperingeffect of the sleeves 15 and 16 as required.

An anchor bolt of the type as described in FIG. 4 is shown in-situ inFIG. 7. The position shown corresponds to an arrangement of anchor boltparts, prior to torquing-up the anchor rod 1. Thus the anchor bolt hasbeen tapped through the hole in the object to be clamped S, is receivedin the receiving socket R, and a distance D exists between the abutmentformed by the expansion body 3 and the end of the outer sleeve 12. Asthe head 2 of the anchor rod 1 is turned the expansion body 3 movesaxially up the anchor rod 1 to reduce the distance D while at the sametime the sleeve 7 is moved into gripping contact with the socket R. Whenthe required setting torque has been achieved the remaining applicationof effort to the anchor rod 1 forces the object to be clamped S intofirm engagement with the receiving material M until the end of the outersleeve 12 touches, or almost touches, the head portion 5 of theexpansion body 3 at which time the inner sleeve 14 abuts, or nearlyabuts, the inner sleeve 11.

The material used for the collapsible sleeve arrangements of the devicesas above described may be made of a metal or of plastics.

Further other modifications and variations will be apparent to thoseskilled in the art which are clearly within the scope of the presentinventive disclosure.

For example manufacturing limitations may be placed on the lengths ofsleeves used in the fixings thereby limiting the lengths of the anchorbolt. To overcome this problem, the embodiments for instance shown inFIGS. 4 or 5, may be modified by dispensing with the sleeve 11 andhaving the sleeve 15 of the same length as the outer sleeve 12. Similarconsiderations apply to the FIG. 6 embodiment the main criterion beingthat throughout the dimensions of the respective sleeves are such thatnone of the effort imparted to the anchor to achieve a fully torqued-upcondition, with the object to be clamped held fast against the barematerial, is lost in loading the sleeves. This means that the sleevesmust be free to slide relative to one another until the above-mentionedset conditions of the anchor bolt, are achieved.

We claim:
 1. An anchor bolt for engagement in a socket in a receivingmaterial to clamp an object thereto, comprising a threaded elongateanchor rod having a head, an expansion body threadedly received on therod in spaced relation to the head and having expanding means drawn intoan expansion sleeve to expand the sleeve into gripping contact with thesocket as the rod is threaded into the expansion body, the expansionbody and the head having opposed spaced abutments, an outer sleevebetween said abutments extending around said rod in spaced relationthereto, said outer sleeve being dimensioned to bridge substantially thespace between said abutments when said bolt is anchored in said socketand said object is pulled tightly against the receiving material, andspacer means on the rod between the rod and the outer sleeve, said outersleeve being slidable over at least part of said spacer means duringthreading of the rod into said expansion body, whereby the space betweenthe rod and the outer sleeve is substantially occupied by said spacermeans when said bolt is anchored in said socket.
 2. An anchor bolt asclaimed in claim 1, wherein said spacer means comprises a coiled springheld between said abutment of said expansion body and said abutment ofsaid rod head.
 3. An anchor bolt as claimed in claim 1, wherein saidspacer means comprises two spaced further sleeves, one of said furthersleeves being press-fit within said outer sleeve for engagement,together with said outer sleeve, with the abutment of said rod head, theother of said further sleeves being arranged for slidable movementwithin the outer sleeve as the rod is threaded into said expansion body.4. An anchor bolt as claimed in claim 3, wherein said one further sleeveis of greater diameter than said other further sleeve and wherein saidouter sleeve is tapered, with the maximum diameter of taper beingadjacent to the abutment of said rod head.
 5. An anchor bolt as claimedin claim 4, wherein said other further sleeve has a longitudinallylocated belled-out portion for progressively straightening the taper ofthe outer sleeve as said rod is threaded into said expansion body.